Crop Profile for Strawberries in California

Prepared: October, 1999

General Production Information



Production Regions

Production Regions. California strawberry production occurs primarily along the central and southern coast, with a small but significant production occurring in the central valley. Fruit production can be divided into five different growing regions. The University has defined these regions as follows (6, 8):

Nursery Production:Nursery stock are produced in two areas of the state, the Central Valley and in high elevation nurseries in Northeastern California. Central Valley nurseries are primarily located in the Northern San Joaquin Valley and Northern Sacramento Valley. High elevation locations are primarily in the state's Cascade mountain range (6, 8). The valley nurseries supply pest/disease free plantings to the high elevation nurseries, as well as other foreign and domestic nurseries.

Production Schedules by Region:Strawberries are harvested in one or more of the growing areas every month of the year, with peak production occurring in late spring. California strawberry yields are over 50% higher than the national average yield and over 4-fold higher than the other states combined (7). As discussed in this crop profile, effective pest management techniques also contribute significantly to the high productivity of the California strawberry industry. The high production of strawberries in California can be attributed to the yield potential of the cultivars grown, the mild coastal climates that are ideal for strawberries, the use of annual production systems that use pathogen- and pest-free planting stock each year, and the intensive management of the crop with a third of the state's acreage being replanted after a one year rotation to an alternate crop. The high level of crop rotation (about 1/3 of the production acreage) and the high level of new plantings each year results in discrepancies in the statistical estimates of strawberry production per year (1, 2, 4, 7, 8). For example, the Department of Pesticide Regulation's Pesticide Use Database (4) often estimates acreage being about twice as large (42,700 acres were in production at some time during 1996) as the actual acreage being actively used for strawberry production in any given season (25,200 acres of strawberry production were initiated in 1996). This is due to the large number of acreage that are active during at least one period during the calendar year, even though much of the acreage was non-producing for the bulk of the year. Production during the winter months, when the calendar year changes, makes these estimates difficult to make using standard techniques.






Cultural Practices

All of California's strawberry acreage is irrigated and most of the crop is grown on an annual basis. Strawberry plants for planting stock are initially grown in the state's nurseries followed by transplantation during the summer or fall. Strawberries are harvested during the following winter, spring, summer and fall. The plants are destroyed after the first harvest season and new plantings are established for subsequent crops. Strawberry plants produce fruit for six months or longer in California. To some extent, berries are picked every month of the year in some area of California.

Nursery Stock Use: California strawberry nurseries produce about 1,000,000,000 runner plants each year, with a farm gate value estimated at about $60,000,000. California is the world's leading producer of strawberry plants. As a result of climate, geography, modern nursery production and postharvest handling systems, and the Strawberry Certification Program administered by the California Department of Food and Agriculture, California nurseries produce high quality strawberry plants that are marketed to nursery and fruit growers throughout the United States and worldwide. Approximately 15% of production is marketed outside California. For plants sold out-of-state, about 40% are sold for nursery planting stock, and the remainder are sold for fruit production purposes (8).

In California, commercial strawberry plant propagation is a multi-year process. Runner plants produced in one nursery propagation cycle are used as planting stock in the next cycle. The first runner generation is produced in a screen-house, with at least three additional runner generations produced in field nurseries. Two or more field propagation cycles occur in low-elevation (less than 500 ft elevation) nurseries in the state's interior valleys (primarily the Sacramento Valley) where climatic conditions result in prolific runner production during a long growing season. A final field propagation cycle occurs in high-elevation nurseries in northeastern California (at greater than 3,200 ft elevation), where temperature and photoperiodic conditions limit nursery runner production but result in increased transplant vigor, productivity, and fruit quality. Nursery location and nursery production practices effect transplant performance in California strawberry fruit production systems (11).

Nursery stock for summer-planted fields comes from low-elevation nurseries located in the Central Valley. These nursery fields are planted in the mid-Spring and harvested at the end of the calendar year. The resulting nursery stock are trimmed, packaged, and kept in cold storage until transplanting into fields the next summer. High-elevation nurseries are used for fall plantings. In these cases, harvested nursery stock are used immediately for transplanting into production fields.

Fumigation:Several weeks before planting, in essentially all but the organically-grown acreage of the state, the soil is fumigated with a combination of methyl bromide and chloropicrin applied under a sealed plastic tarp, which is removed after about of 5 days (120 hours). Plants are set by hand into deep, narrow holes on pre-moistened beds. If bed fumigation is used, plants are set through holes in the plastic at least two weeks after fumigation, and the plastic mulch stays in place until the plants are removed. Methyl bromide is scheduled for phase out over a 4 year period due to environmental concerns and will be unavailable after 2005. The consequential rapid replacement of this pest management tool that is currently essential to the industry's productivity will certainly have a major impact on the cultural practices employed by the industry by the middle of the next decade.

Mulch: Mulch can be used to ensure that the strawberries and plant foliage are separated from the ground. This reduces pathogen transfer, enhances soil warming and improves water management. If mulch is used, it is put on immediately after planting. Typically, clear polyethylene mulch is applied to warm the soil, increase early plant growth, and keep the berries off the damp ground. The color of the tarp is important for efficacy and productivity. In Southern California, use of black or colored tarps can reduce weed populations but result in a 10% yield reduction due to less effective soil warming.

Harvesting: The grower/shipper or shipper assumes control of all operations related to harvest. Once harvesting commences, hand-harvesting continues for several months on a 3 to 5 day cycle. This continual harvesting ceases when the productivity of the field diminishes significantly.

Strawberries are harvested carefully by hand and are not subject to washing at the time of harvest. Harvested strawberries are placed in trucks, within an hour or two of picking, which transport the strawberries to a cooling facility. All strawberries are cooled, usually within 1 to 4 hours after harvest. Strawberries are typically forced-air cooled at temperatures of 34F. Cooling reduces decay and prolongs the fruits shelf-life.

Nearly all strawberries are shipped to the market in refrigerated trucks, and temperatures in the range of 34-36F are maintained during shipment. The following examples are provided to indicate typical times associated with the harvesting, cooling, and shipping operations:



Time :

Harvest Activity

Day 1 Harvest: Delivery to yard and cooling (1-4 hours).

Day 2-6 Shipping within the United States:

To Seattle - 1 day
To Denver - 2 days
To Chicago - 3 days
To New York/Boston - 4 days

Receiving dock to supermarket: 1 day

Day 2-6 Shipping outside the United States:

Canada - 3-5 days
Mexico - 3-5 days
Japan (air freight) - 1 day

Varieties: Over a dozen major cultivars of strawberries are grown commercially in California. Strawberry cultivars are developed based on several factors including desired day length, fruit size, flavor, appearance, and vigor. Cultivars vary in their susceptibility to some pests and abiotic disorders. The Camarosa strawberry variety is planted in 46% of the state's acreage, with the Selva variety planted in 25% of the acreage. The Chandler variety, which used to account for 40% of the acreage in 1994, is now less than 3% of the production. Proprietary varieties account for 23% of the acreage. The Diamante and Aromas varieties are increasing in popularity (1, 8).

The primary cultivar grown in the central and southern coastal regions is the Camarosa, with this variety accounting for 96%, 72%, and 80% of the acreage in the Orange/San Diego, Oxnard, and Santa Maria districts, respectively. In contrast, this variety is only 10% of the Watsonville/Salinas district and 22% of the San Joaquin Valley district. The Selva and proprietary varieties are primarily used in the Watsonville/Salinas district whereas the Chandler variety is over 78% of the production in the San Joaquin Valley (1, 8). Other cultivars that are grown include the Seascape, Aromas, and Diamante. Specific planting and harvest seasons vary from one growing area to another; however, two planting seasons are used in most areas. Summer plantings usually are made in mid to late summer and fall plantings from mid-October to early November. Summer plantings are grown in the San Joaquin Valley and Southern California.

Cultural Practices: Decisions related to various cultural practices are made daily by growers. Decisions related to field selection, soil nutrient supplements, and cultivars are made well in advance of planting. Fields are graded and planting beds designed to allow proper drainage and irrigation. Clean tillage, raised beds, plastic mulches and water management are all aspects of a systems approach practiced by California strawberry growers.

Crop Rotation: Strawberry fields are sometimes rotated with cover crops such as rye or barley, or another cash crop such as beans, broccoli, lettuce, and cauliflower to reduce pest populations and improve soil structure. Time is allowed from one crop to another to allow crowns from the previous crop to decompose completely. In the south and central coast areas, where land and water costs are high, cover crops are not economically feasible (6, 8).

Sanitary Techniques: Growers use high quality pathogen-free cultivar transplants and the Strawberry Certification Program sponsored by the California Department of Food and Agriculture to help maintain their field free of pathogens. The certification program is based on nursery soil treatment with methyl bromide prior to planting. Growers also practice field sanitation, working the "cleanest" (pathogen free) fields first, rinsing the equipment with hot water to remove soil and plant debris before working another field. Weeds are removed from and around strawberry fields before they produce seed. Growers also try to ensure that manure or other organic amendments added to the fields have been properly composted or sterilized (6).

Pesticide Application Practices: All applications of pesticides in California are under the control of the growers, and/or their Pest Control Advisor (PCA), or Pest Control Operator (PCO). Growers, PCAs, and PCOs work closely to insure that only registered pesticide products are used and that they are applied in compliance with all state and federal laws, rules and regulations, and labeled recommendations.

Communication between growers, PCAs, and PCOs is maintained during the planting and production periods through frequent field visitations by grower representatives and/or their PCAs. The applicator must inform all affected parties in close proximity to the intended treated area (e.g., harvesting crews, weeding crews, irrigators, etc.) of their intent to apply pesticides in advance of the application and must also post fields and file post-application paperwork with the appropriate state and/or federal agency. Closed systems are also mandatory for the application of Toxicity Category I pesticides in California.

Virus Reduction. Because insect-vectored viruses are so devastating to strawberries, cultural methods have been changed radically to minimize the serious impact of these many viruses. All varieties are produced through a meristem program to remove viruses. Nursery production fields are far removed and isolated from strawberry fruit production regions. In most production regions, annual plantings are used to minimize virus impacts on fruit production, as well as resistance management for insects, mites and fungal diseases.

Organic Production: Organically grown strawberry production is currently less than 0.1% of the total acreage. Reports on production yields per acre from organic fields range from 25% to 60% of the conventional yields (8).





Insect Pests

It is important to note that all discussions related to insect control are based on pest management strategies utilizing certified pest/disease free nursery stock growing in soil treated with methyl bromide/chloropicrin.



Twospotted Spider Mite
Tetranychus urticae

Damage:The twospotted spider mite is a serious pest of strawberries in all California growing areas. Twospotted spider mite damage to strawberries is expressed as stippling, scarring, and bronzing of the leaves and calyx. Twospotted spider mite feeding seriously interrupts photosynthesis and is particularly damaging during the first 4 to 5 months following transplanting, in late summer, fall, or early spring, depending on the growing region. Mite feeding during this critical period of plant growth substantially reduces berry numbers per plant and overall yield. Plants are less sensitive to mite feeding after initial berry set but yield loss can be significant at all mite infestation levels exceeding one mite per leaflet. Substantial yield loss can result from densities exceeding 5 to 10 mites per leaflets until mid-spring, and 20 mites per leaflet or more thereafter. Plants that sustain infestations of greater than 75 mites per leaflet may become severely weakened and appear stunted, dry, and reddish.

Description of Pest: Twospotted spider mites are typically found on the bottom surface of strawberry leaves. Mating and egg laying behaviors are typically observed in all coastal strawberry growing regions year round. The highest mite populations are often observed following the spring fruit harvest, and this peak is typically followed by a rapid, natural decline in mite density.

Monitoring: Growers monitor the twospotted spider mite pressure within the field to determine if they are being maintained below economically injurious levels. Vigorous plant growth during the first 4 to 6 months following fall transplant is a key factor in strawberry production. More than 80% of strawberry acreage is fall-planted and mite control during the first 4-6 months is critical when the effectiveness of many technologies (i.e. predators, AVID, VENDEX) is marginal. During this critical period, mite feeding is extremely damaging and the established economic threshold is five or fewer mites per mid-tier leaflet. Tetranychus cinnabarinus is a close relative of the twospotted spider mite and should be identified correctly. It is commonly found at low densities but has only been reported as damaging in San Joaquin Valley growing regions.

Controls:

Cultural:

Biological:

Chemical:
Twospotted spider mites have a history of developing resistance to miticides rapidly when a miticide is applied repeatedly to the same population. Alternating the use of miticides that have different modes of action helps reduce the development of resistance to a specific miticide. Organophosphate, carbamate, and pyrethroid insecticide applications can stimulate twospotted spider mite outbreaks by disrupting the balance with beneficial insects.

The following active ingredients are not currently registered for use on strawberries but are needed tools as soon as possible. An expedited registration is encouraged by the industry.



Lygus Bugs
Lygus hesperus

Damage. Lygus bugs are one of the causes of irregularly-shaped, cat-faced strawberries. Lygus bugs damage fruit by puncturing individual seeds; this, in turn, stops development of the berry in the area surrounding the feeding site. Lygus bugs are a serious pest in central strawberry-growing areas (interior valleys, central coast, Santa Maria Valley regions) where strawberries are typically grown past May and through the summer months, but are rarely pests in southern California, where the fresh market berry harvest is generally complete by the end of May.

Description of Pest. Adult Lygus bugs are about 0.25 inch long. Immature forms of lygus bugs are as damaging as adults. The larger nymphs (immature forms) are pale green and look somewhat like an aphid. They can be distinguished from aphids by their more rapid movements. Overwintered lygus bugs lay eggs in weeds in January which hatch in March.

Monitoring. Monitoring fields for nymphs and adult lygus bugs is critical in their control. There are two major monitoring periods for lygus bugs in strawberries grown in central and northern California. Infestations in southern California strawberry fields are rare. Early in the season, growers monitor for the first appearance of lygus nymphs on weed hosts. Lygus bugs can be active all winter. Monitoring for adults begins in mid-April to detect when adults first appear in the field.

Controls

Cultural:

Biological:

Chemical:
Chemical treatments are applied to control lygus when they are at the most susceptible first and second instar nymph stages. Insecticides applied to later nymphal stages and adults are much less effective. Short residue insecticides do not control lygus bugs, necessitating repeated applications.



Cyclamen Mite
Steneotarsonemus pallidus

Damage. The cyclamen mite is an important pest of central coast strawberries. It has become a less significant problem as fewer strawberry fields are retained for multiple season use due to the shift to annual plantings. Leaves heavily infested with cyclamen mites become severely stunted and crinkled, resulting in a compact leaf mass in the center of the plant. Feeding on flowers can cause them to wither and die. Fruit on infested plants is dwarfed, and the seeds stand out on the flesh of the berry. When uncontrolled, this mite can prevent plants from producing fruit.

Description of Pest. At low population densities, cyclamen mites are usually found along the midvein of young unfolded leaves and under the calyx of newly emerged flower buds; when populations increase, these mites can be found anywhere on nonexpanded plant tissue. Cyclamen mites are primarily pests in second year plantings and are not visible to the naked eye. Adult female cyclamen mites overwinter in the strawberry crown.

Monitoring. Growers monitor unfolding leaves to identify the presence of mites. When one cyclamen mite/10 leaves is identified chemical treatment is indicated.

Controls

Cultural:

Biological:

Chemical:
To control cyclamen mites, a high rate of water per acre (300-500 gal) is necessary to soak the unfolded leaves and immature flower buds located in the crowns. Growers sometimes remove or treat infested hot spots by hand-sprayer to suppress infestations to avoid treating the entire field. In nurseries, early-season control before the plant canopy closes over is critical. Use of certified pest and disease free nursery stock is a key to control.



Aphids

Strawberry Aphid: Chaetosiphon fragaefolii
Melon Aphid: Aphis gossypii
Green Peach Aphid: Myzus persicae
Potato Aphid: Macrosiphum euphorbiae

Damage. Aphid damage to berries occurs in all growing regions. Aphid damage is less critical in the central coastal region where aphid populations typically are not as high. Aphids occasionally cause yield losses in California strawberries because of their honeydew production. Honeydew deposits on fruit cause sooty molds to develop and the white skins shed by aphid nymphs to stick to the fruit. This contamination renders the fruit unmarketable as fresh fruit. Also, aphids transmit several viruses that can cause significant economic losses in perennial strawberries. Aphid control is also crucial in strawberry nurseries to reduce the possibility of virus transmission.

Description of Pest. Populations of aphids usually begin to reach potentially damaging levels in California during late January or February. Populations undergo a natural decline, usually to noneconomic levels, during May and June. Strawberry aphid, typically the most common species of aphid found on strawberries, is pale green to yellowish in color. The melon aphid, the second most common species on strawberry, is often the first to migrate into the strawberry fields each season. Green peach aphid and potato aphid rarely account for more than 10% of the total aphid populations in the field. The potato aphid is much larger than the other species and has both a pink form and a green form in California.

Monitoring. Growers measure the percent aphid infestation by sampling trifoliate leaves. If infestation reaches a threshold, chemical treatment becomes necessary to minimize economic losses.

Controls

Cultural:

Biological:

Chemical:
Chemical treatments are made when aphid pest pressure reaches a trigger level (sometimes this trigger is when 30% of young trifoliated leaves are infected). Trigger levels can be selected to minimize the impact on beneficial insects in the fields.



Root Weevils

Cribrate Weevil: Otiorhynchus cribricollis
Woods Weevil: Nemocestes incomptus
Black Vine Weevil: Otiorhynchus sulcatus
Fuller Rose Weevil: Pantomorus cervinus

Damage. Root weevil larvae feed on the roots of strawberry plants and can completely devour small rootlets and destroy the bark and cortex of larger roots. Soon after feeding begins, plants wilt because the roots can no longer provide moisture for leaves. It is not uncommon to find weevil larvae that have penetrated into the lower portion of the plant's crown. These pests caused major economic damage in the 1950s prior to the onset of methyl bromide use. As a result, root weevils are anticipated to become an increasingly important pest in the next few years as methyl bromide is removed from the marketplace.

Description of Pest. Adult root weevils are beetles. They feed at night and hide around the crowns of plants during the day; they cannot fly. Adults feed on foliage and remove large scallops from the leaves. Such leaf damage is a good indication that weevils are present, but is not economically damaging to the plants. The adults, nearly all females, emerge in late spring or summer and feed on strawberry foliage. Eggs laid on the plants, after hatching, work their way into the soil and feed on strawberry roots and crowns. In spring, they resume feeding and can cause extensive damage before they pupate. Root weevils have a single generation each year.

Monitoring. Observations for infestation such as crown damage. Though some damage is acceptable, severe damage triggers control methods.

Controls

Cultural:

Biological:
No known biological controls of root weevils.

Chemical:



Western Flower Thrips
Frankliniella occidentalis

Damage. Damage from thrips has increased in recent years. Damage, which rarely became economically significant in past years, is impacting yield and quality. When very abundant, more than 10 thrips per blossom, fruit can be seriously discolored (bronzed). Thrips feeding on strawberry blossoms causes the stigmas and anthers to turn brown and wither prematurely, though not before fertilization has occurred. As fruit develops, thrips feeding may cause a russeting of the fruit around the cap, but this type of injury is seldom economic.

Description of Pest. Western flower thrips are slender, very small insects. Flower thrips populations build up on alfalfa, weeds, and other vegetation in spring, and then move from these hosts when they are cut or dry up.

Monitoring. Control is necessary when western flower thrips are very high (typically a trigger of 10 thrips per flower).

Controls

Cultural:

Biological:

Chemical:
Chemical control methods are only necessary when thrips become very high.



Cutworms

Black Cutworm: Agrotis ipsilon
Roughskinned Cutworm: Athetis mindara

Damage. At times serious damage can occur to the plant crown. On fruit, during harvest, cutworms can cause pronounced holes. Early-season damage by newly hatched cutworms generally appears as small, webless perforations in the newly expanding crown leaves. As larvae grow, they begin their characteristic stem cutting along with chewing larger, irregular holes in the foliage. Damage by cutworms tends to be more serious in fields where bug-vacs have been used, but the reasons for this are not known and bug-vacs are rarely used.

Description of Pest. The black cutworm, also called the greasy cutworm, is the primary cutworm pest of strawberries in most growing areas but other species are found in damaging numbers on occasion. Most damage occurs in fall and spring, with the fall attack being more destructive. Migration of adult moths can also occur following harvest of other hosts, such as lettuce, in nearby fields.

Monitoring. Monitoring for cutworms is done visually or by trapping. Damage to fruit particularly is monitored.

Controls

Cultural:

Biological:

Chemical:



Beet Armyworm
Spodoptera exigua

Damage. The greatest damage from beet armyworm occurs to summer and fall-planted strawberries in the southern growing regions of the state. Newly hatched beet armyworms are foliage feeders, skeletonizing the upper or lower leaf surfaces adjacent to their egg mass. Larger larvae can attack the crowns of young plants, killing them. Young larvae feed on foliage before attacking berries. Larger armyworms feed directly into the berries. Smaller armyworms will often feed on the shoulder of the berry.

Description of Pest. Fall populations of armyworm moths will often fly into strawberry fields to lay eggs. Newly hatched armyworms are often green in color and feed in groups, skeletonizing the undersides of leaves.

Monitoring. Treatments are made while armyworms are still young. If large numbers of predators are present, treatments may be delayed to determine if the armyworms might be controlled by the natural enemies.

Controls

Cultural:

Biological:

Chemical:



Whiteflies

Iris Whitefly: Aleyrodes spiroeoides
Strawberry Whitefly: Trialeurodes packard
Greenhouse Whitefly: Trialeurodes vaporariorum

Damage. Whiteflies are always present in strawberry fields, but rarely build up to damaging numbers causing economic impact. Damage is typically limited to late season, sporadic outbreaks but their occurrence has become more widespread in the past few years for unknown reason. This is especially true of greenhouse whitefly. Like strawberry aphids, whiteflies suck plant juices and at high population levels can excrete large amounts of honeydew on which a sooty mold fungus grows. Whiteflies do not carry and transmit viruses of strawberry.

Description of Pest. Adult whiteflies are small insects. Whiteflies generally overwinter in the immature stage on the leaves of strawberries. Adults begin laying eggs on the undersides of leaves. Due to the relatively short life cycle of 4 to 5 weeks, there are several overlapping generations during the year.

Monitoring. Treatments are rarely necessary except along dusty road edges or if whitefly biological controls are disrupted by the use of a non-selective pesticide. Treatment is only necessary when honeydew becomes apparent, as has occurred more recently in the past few years.

Control

Cultural:

Biological:

Chemical:



Secondary Insect Pests

It is important to note that all discussions related to insect control are based on pest management strategies utilizing certified pest/disease free nursery stock growing in soil treated with methyl bromide/chloropicrin.



Cabbage Looper
Trichoplusia ni

Damage. Young cabbage looper larvae feed primarily on the undersides of leaves, skeletonizing them. High populations can damage fruit but this is very uncommon. The cabbage looper is becoming more a pest challenge in the southern growing regions.

Description of Pest. Loopers have a characteristic arch to their back as they crawl. Eggs are similar in appearance to corn earworm eggs, but flatter.

Monitoring. When monitoring for other pests, growers watch for evidence of looper feeding: leaflets with holes, feces, and caterpillars feeding at the edge of a hole. If larvae are larger instars, an organophosphate may be needed to control them.

Controls

Cultural:

Biological:

Chemical:



CORN EARWORM
A.k.a.: Tomato Fruitworm, Cotton Bollworm

Heliothis zea
Helicoverpa Zea

Damage. The south coastal zone is the only location where corn earworms can become a significant problem. Problems are most severe when the field is in close proximity to a corn or tomato field. Corn earworms damage strawberries by burrowing into fruit. Although there are several generations each season, only larvae of the first generation attack winter strawberries. Entrance holes made by early instar larvae are not visible, and the fruit must be cut to determine their presence. Contamination of the fruit prevents it from being marketed as whole fruit. Federal tolerance currently requires downgrading to juice stock if a single 7 mm or larger larva is found per 44 pounds of fruit (about 1,100 berries).

Description of Pest. Adult corn earworms are light grayish brown moths. Larvae typically feed within the fruit. Mature fruit containing large larvae appear seedy and develop a shrunken surface with one or more brown patches. The time needed to complete a generation is temperature dependent, but often takes about 1 month.

Monitoring. Growers monitor yearly for corn earworm in the south coast region using pheromone traps. Pheromone traps help monitor emergence and flight activity of the moths in late February/early March. When unparasitized eggs are found in the strawberry field, growers consider chemical treatments. Outbreaks of corn earworms often occur in years when warm air currents associated with El Niño conditions allow moths to migrate from the south. Monitoring is increased under these conditions.

Controls

Cultural:

Biological:

Chemical:



European Earwig
Forficula auricularia

Damage. Earwigs are a pest of the south coast region. Earwig feeding results in small deep holes in the fruit that can only be distinguished from slug damage by the absence of slime.

Description of Pest. Earwigs feed at night and can be found hidden around crowns of plants during the day. They are slender brown insects, about 0.5 to 0.75 inch long. They have a conspicuous pair of pincers attached to back end of the abdomen. The pest becomes most destructive as nymphs approach maturity from April to July.

Monitoring. When significant fruit splitting occurs, applications of bait are needed if earwigs are present

Controls

Cultural:

Biological:
No significant biological controls are known.

Chemical:



Hoplia Beetle
White Grubs
Hoplia oregona

Damage. Hoplia larvae, or white grubs, typically feed on perennial grasses but may attack strawberries feeding on the roots of strawberry plants. Small rootlets may be devoured and the bark and cortex of larger roots destroyed. Injured plants wilt as the roots can no longer provide moisture from leaves. Hoplia may be found throughout California but is most frequently found in the Central Valley. Damage is rarely seen in fumigated fields. Hoplia larvae has become a serious pest in nonfumigated fields in the Central Valley, where it has killed half the plants in heavily infested fields.

Description of Pest. Adults are brown beetles that are active for about two weeks after emerging in May, feeding on plants, mating and laying eggs on the soil. Adults are inconspicuous because they fly poorly. Hoplia larvae are white grubs that feed on plant roots for up to two years before pupating. Soil fumigation has kept white grubs from becoming a problem.

Monitoring. Growers monitor the fields for evidence of beetles or damage from larvae. Injured plants often develop in a small circular area. Though some damage is acceptable, sever damage triggers control methods.

Controls

Cultural:

Biological:
No known biological controls of hoplia larvae.

Chemical:



Garden Sympgylan
Scutigerella immaculata

Damage. Garden symphylans damage plants by feeding on roots, thus retarding plant growth. They are usually only a problem in fields that were not fumigated, or if the fumigation was ineffective.

Description of Pest. Garden symphylans are slender and white. They occur mainly in moist soils with good structure and a high organic matter content, and are often associated with debris from a previous crop that is not completely decomposed. Since these pests rarely leave the vicinity of their infestation, they return to damage the same area every season so infestations spread slowly.

Controls

Cultural:

Biological:
There are no known biological controls that specifically target the garden symphylan.

Chemical:



Garden Tortrix
Ptycholoma (Clepsis) peritana

Damage. Contamination of south coast fields just before the berries are sent to the processors during late June and July can be a serious problem. Garden tortrix larvae generally feed on dead and decaying leaves and fruit usually causing no significant damage. However, as the population increases and the plant canopies close in, more ripening berries settle down into the trash among the tortrix larvae. When this happens, larvae will often spin a nest in creases along the berry's surface and chew small, shallow holes in the berry, incidental to their scavenging. With the higher populations often attained by late spring or early summer, significant fruit losses can result from both larval contamination and secondary rots invading the feeding holes.

Description of Pest. The adult has the typical bell-shaped tortricid moth wings while at rest. Adults aren't usually seen until March or April. Larvae hatching from eggs laid in spring on older leaves move down into the trash where they feed on dead and decaying leaves. They construct shelters by tying bits of trash together. As a result of overlapping generations, all stages are generally present in spring and summer.

Monitoring. Late May, June, and early July are generally when treatments may be required. Chemical control is difficult to achieve due to the location of the larvae down in the litter beneath the protective canopy of strawberry leaves.

Control

Cultural:

Biological:
There are no known biological controls that specifically target garden tortrix.

Chemical:



Saltmarsh Caterpillar
Estigmene acrea

Damage. Saltmarsh caterpillar is occasionally a pest in the Fall in southern growing regions when hot temperatures prevail. When saltmarsh caterpillars first hatch, they remain clustered and feed on the undersides of the leaves where the egg mass was laid. They skeletonize the foliage. As caterpillars grow, they eat holes in the leaves. This type of damage is generally of little or no concern, but the caterpillars can also make superficial bites in the fruit, causing significant economic loss.

Description of Pest. Adult moths are white with orange abdomens. Mature caterpillars are almost 2 inches long. Emerging moths lay their round, shiny eggs in several rows forming a neat cluster on the undersides of leaves. There are several generations each year.

Controls

Cultural:

Biological:

Chemical:



Vinegar Fly
Drosophila melanogaster and other species

Damage. Vinegar flies (a.k.a., fruit fly) are primarily a problem in strawberries picked for processing. In general, the vinegar fly can be a problem from the Oxnard Plain south. Because this fruit is allowed to ripen in the field to allow easy removal of the calyx and core of the strawberry during picking, the harvest interval is increased and the fruit becomes more susceptible to infestation. Vinegar flies are attracted to very ripe or damaged fruit in the field where they lay their eggs. Eggs and larvae are primarily a contamination problem.

Description of Pest. Vinegar flies, also known as fruit or pomace flies, are small, yellowish flies. This pest has become more important in recent years with an increasing need for alternative control methods.

Monitoring. No monitoring or treatment guidelines exist for vinegar flies in strawberries, although yellow sticky cards are sometimes used to monitor adult fly populations. Adults and their offspring may be monitored with fermented fruit traps consisting of a container filled with overripe fruit covered with an inverted funnel.

Controls

Cultural:

Biological:
There are no known biological controls that specifically target vinegar flies.

Chemical:
Vinegar fly eggs and larvae in the berries cannot be killed using insecticides. Treatments are applied to kill adult flies.





Diseases

It is important to note that all discussion related to disease control are based on pest management strategies utilizing certified pest/disease free nursery stock growing in soil treated with methyl bromide/chloropicrin.



Botrytis Fruit Rot
Botrytis cinerea

Damage. Botrytis Fruit Rot or Gray Mold is the most common and most serious disease of strawberry fruit in California. This disease can affect all parts of the plant. Both fruit and nursery production are impacted. It is estimated that botrytis damage can reduce the value of California's harvest by 30 to 40% compared to production where chemical methods of pest management are not practiced (8). This loss can be as high as 50% to 60% under conditions of severe disease challenge and when infestation in the field reaches this level the economic loss is 100%. Botrytis fruit rot occurs in all growing areas and can cause losses of fruit both in the field and after harvest. Infected berries maintain their original shape and take on a velvety grey brown coat of mycelium and spores. Initially, rotted areas are soft and mushy, becoming leathery and dry in the absence of high humidity. Direct infection of the berries also occurs if berries are exposed to free water. These infections develop in the same manner as flower-infected berries, but differ in that multiple initial lesions may appear anywhere on the berry's surface. For nurseries, damage to petiole and leaf tissue can be significant.

Description of Disease. Botrytis fruit rot is widespread. It can infect flowers on strawberry plants when spores landing on them are exposed to free water and cool temperatures. Infections can either cause flowers to rot or Botrytis can become latent. Latent infections resume activity on the berry later in the season. Both green and red berries are susceptible, but ripening berries rot faster. During the growing season, the fungus is constantly present.

Monitoring. Inoculum density and environmental conditions conducive to disease development (i.e., rain and cool temperatures) determine when fungicide applications are needed. Because these conditions are usually seasonal, a protective application of a fungicide is used typically to prevent germination of spores when conditions are ideal for disease development. Spray schedules thereafter are set according to disease pressure and environmental conditions.

Controls

Control of Botrytis fruit rot ranges from repetitive fungicide treatments with no cultural control to intensive cultural methods with limited or no fungicide applications. Environmental conditions in various microclimates play an important role in determining control strategies. It is crucial to avoid or delay the onset of fungicide resistance. It is common practice to rotate the use of fungicides between chemicals that represent different chemical classes.

Cultural:

Biological:
No biological control agents are currently available to the industry that target botrytis fruit rot. Trichoderma harzian is being developed as a possible biological control agent (to be registered under FIFRA) but has not been commercialized yet.

Chemical:
It is crucial to avoid or delay the onset of fungicide resistance. As a result, fungicide applications are usually rotated through several active ingredients during a season, with fungicides of different chemical classes being applied in sequence. Use of repeated applications of the same or related fungicide is avoided. Due to the differences in price of the available fungicides, this approach can be financially challenging. Tank mixing of fungicides is also common, lowering the application rate required of any single fungicide.



Verticillium Wilt
Verticillium dahliae

Damage. Verticillium wilt is becoming an increasingly important disease in California strawberries. It is slow growing but, once established, it is extremely difficult to eradicate. Spread of the disease from contaminated planting stock is an increasing concern, making control of this disease at the nursery stage crucial. The pathogen is a soil-borne fungus and the loss of the methyl bromide/chloropicrin combination fumigant is anticipated to have a significant adverse effect by increasing the prevalence of Verticillium wilt. Verticillium wilt causes outer leaves to exhibit marginal and interveinal browning, followed by eventual collapse. Inner leaves remain green but are stunted and exhibit brownish black streaks or blotches. This last symptom distinguishes this disease from crown rot. Outbreaks of the disease typically result in observable "streaks" or "stripes" within the field.

Description of Disease. The fungus is not host specific and infects many weed species and crops worldwide. It is especially destructive in semi-arid areas where soils are irrigated. Inoculum densities may be high following planting of susceptible crops. Disease severity is greater when excessive levels of nitrogen are used.

Monitoring. The most common indication of Verticillium wilt is the observation of brown or dead outer leaves with green inner leaves.

Control

Cultural:

Chemical:



Rhizopus Fruit Rot
Rhizopus spp.

Damage. The fungus lives on and helps break down decaying organic matter. It invades strawberries through wounds and secretes enzymes that degrade and kill the tissue. Under conditions of high relative humidity, the berry rapidly becomes covered with a coat of white mycelium and spores. After high temperatures, the disease can become quite destructive. Outbreaks of the disease have caused 20 to 35% loss in production in the Oxnard plain.

Description of Disease. Initial infections appear as discolored, water-soaked spots on fruit. These lesions enlarge rapidly, releasing enzymes that leave the berry limp, brown, and leaky. The sporangiophores develop black sporangia, each containing thousands of spores. When disrupted, these sporulating berries release a cloud containing millions of sporangiospores.

Monitoring. Observations of twig die-back indicates presence of the disease.

Controls

Cultural:

Biological:
There are no biological control techniques specific to Rhizopus Fruit Rot at this time.

Chemical:
There are no chemical treatments that are highly effective against Rhizopus Fruit Rot but the following chemicals can be used.



Powdery Mildew
Sphaerotheca macularis

Damage. Powdery mildew is mostly limited to the coastal growing regions and northern nurseries, and causes very little damage in inland growing regions. Infestations during the 1990s have been the worst in the central coastal region. Some of the differences in vulnerability are due to the different varieties that are grown in these different regions. Infected flowers produce deformed fruit or no fruit at all. Severely infected flowers may be completely covered by mycelium and killed. Infected immature fruits become hardened and desiccated, often resulting in the observation of fruit "bronzing". Infected leaves initially produce small, white powdery colonies on the undersides of leaves.

Description of Disease. Colonies of powdery mildew multiply to cover the entire lower leaf surface, causing the edges of the leaves to roll up. Purple-reddish blotches appear on the upper and lower surface of leaves. Infected mature fruits become seedy in appearance and support spore-producing colonies that look powdery and white. The disease overwinters as mycelium on leaves in California, so it is most likely introduced into the field through planting material or spores from neighboring fields. Ideal conditions for infection are dry leaf surfaces, high relative humidity, and cool to warm temperatures. Because of this, the disease is mostly limited to the coastal growing regions and northern nurseries, and causes very little damage in inland growing regions.

Monitoring. Early signs of the disease are monitored since preventative control is most effective. Applications are often tied to models based on meteorological observations.

Control

Cultural:

Biological:



Chemical:
Controlling the disease on leaves with fungicides does increase yields, though losses are almost entirely due to infection of flowers and fruit. Flower and fruit infections generally are the result of severe leaf infections. Protective fungicides are used to protect flowers and fruit. Fungicides are applied about 1 month after planting and again 3 to 4 weeks later. Additional treatments are made when plants begin to bloom.



Phytophthora Crown Rot & Root Rot
Phytophthora cactorum
Phytophthora citricola
Phytophthora parasitica
Phytophthora megasperma

Damage. Phytophthora is a genus of soil-borne fungi. Stunting is common. Initially, the youngest leaves on the strawberry plant begin to wilt and also may turn bluish green in color. Plant collapse also occurs rapidly or slowly, depending on the Phytophthora species involved. When infected plants are cut open, a brown discoloration can be seen throughout the crown tissue. Phytophthora species also attack root tissue, causing a brown to black root rot.

Description of Infection. Motile spores (zoospores) are released into the soil and swim to plant tissue when the soil becomes saturated with water for prolonged time periods. When the soil drains and dries, zoospores either encyst or die. Mycelium in infected tissues make resistant structures that overwinter and survive harsh conditions.

Control

Cultural:

Chemical:



Common Leaf Spot
Ramularia tulasneii

Damage. Common leaf spot is the most important of the strawberry leaf spot diseases in California. The disease is not as important as it has been in previous years, particularly in south coast regions. However, the disease can decimate the productivity of fields if unchecked. The pathogen is introduced into fruit production fields as small, black sclerotia on infected nursery material. Germination of sclerotia is initiated by fall and winter rains or sprinkler irrigation. Spores are dispersed by wind-driven rain. Common leaf spot can be a problem in all nursery and fruit production areas, but is usually less prevalent in the drier interior valleys and southern growing regions.

Description of Infection. Small, deep purple spots initially appear on the upper surface of leaves, with the center portion of the lesion turning brown then grey to white depending on the age of the leaf and environmental conditions. Numerous spots may coalesce to kill the leaf. On petioles, stolons, calyxes, and fruit trusses, elongated sunken lesions may form and interfere with water transport in the plant, weaken the structure, or allow invasion by secondary organisms.

Controls

Cultural:

Chemical:
Protective fungicides are effective if used at the appropriate time. Applications are made in anticipation of warm, damp weather.



Anthracnose
Colletotrichum acutatum

Damage. Anthracnose is a sporadic disease that is most common in wet, El Nino years , especially in Southern California. Flowers, ripe and unripe fruit can be affected. Warm or cool, wet conditions favor the development of fruit and stem rot. Anthracnose can also cause root rot and crown rot. The worst problems from this disease come from nursery stock.

Description of Disease. On fruit, light tan to light brown water-soaked lesions develop and turn into sunken black lesions. Dark elongated fusiform lesions appear on petioles and runners, and often girdle the stem. Fungus overwinters in plant debris or alternate weed hosts.

Control

Cultural:

Biological:
There are no specific biological control methods for anthracnose.

Chemical:



Secondary Diseases

It is important to note that all discussion related to pest control are based on pest management strategies utilizing certified pest/disease free nursery stock growing in soil treated with methyl bromide/chloropicrin.



Leather Rot
Phytophthora cactorum

Damage. Leather rot of strawberry fruit is not common on most annual plantings of strawberries in California. Plantings held for 2 or 3 years, however, can be infected by the leather rot pathogen. Infected fruit is bitter and has tough areas where infections appear.

Description of Infection. All stages of fruit are susceptible to leather rot. The fruit appears dull and lifeless, ranging in color from light purple to ripe red. The external infected area becomes tough, while the internal tissue is somewhat softer with vascular tissue turning dark brown. The fruit tastes bitter.

Controls

There are very few options that are effective in control of leather rot. Though this disease is currently of little concern, the loss of methyl bromide may have a significant impact on the onset of this disease.

Cultural:

Biological:
There are no biological control methods that target leather rot.

Chemical:
This disease is largely controlled through the widespread use of methyl bromide. The removal of this chemical from the marketplace is likely to cause an increase in the occurrence and severity of leather rot.



Mucor Fruit Rot
Mucor spp.

Damage. Mucor Fruit Rot is not a commonly seen disease in California strawberries though outbreaks do occur, often in conjunction with outbreaks of Rhizopus Fruit Rot. The disease invades the fruit through the slightest wound. Under conditions of high humidity, the berry becomes covered with a coat of tough, wiry mycelium and black spore-bearing structures. High temperatures trigger onset of the disease.

Description of Infection. Like the fungus that causes Rhizopus fruit rot, Mucor fruit rot invade the fruit through wounds. The fungus secretes an enzyme that rapidly results in a leaky fruit rot. The fungus produces millions of airborne spores that are favored by warm, moist conditions. Because the fungus lives on dead and decaying organic matter, field sanitation is important.

Control

Cultural:

Chemical:
Though protective, broad-spectrum fungicides are available for use to control Mucor fruit rot, they are rarely used to target this disease. Treatments are made before the advent of cool to warm, moist weather after fruit set has begun.



Angular Leaf Spot
Xanthomonas fragariae

Damage. The adverse impacts of angular leaf spot are increasing. The disease is a severe problem in all nursery locations and is becoming more of a problem in fruit production regions such as the central and south coast. The disease is favored by cool, moist days with cold nights near freezing. Infection first appears as minute, water-soaked spots on the lower surface of leaves. The lesions enlarge to form translucent, angular spots that are delineated by small veins and often exude a viscous ooze, which appears as a whitish and scaly film after drying. As the disease progresses, lesions coalesce and reddish brown spots, which later become necrotic, appear on the upper surface of the leaves. A chlorotic halo usually surrounds the infected area.

Description of Disease. This bacterium is not free living in soil. It can, however, overwinter in soil on previously infected plant material. Transmission is by splashing water. It is host specific and highly resistant to degradation. The disease can persist in the soil for long periods of time. It is killed by methyl bromide/chloropicrin mixture used as a preplant fumigant, so it is very likely that most initial infections in fields that have been fumigated originate from contaminated plants. Lesions on the leaf surface serve as a source for secondary inoculum and cells are dispersed by splashing rain or overhead irrigation. Although uncommon in California, Xanthomonas fragariae can cause vascular collapse and can be confused with phytophthora crown rot and root rot, Colletotrichum crown rot and Verticillium wilt. This symptom initially appears as a water-soaked area at the base of newly emerged leaves. Shortly after, the whole plant suddenly dies, much like plants infected with crown rot.

Controls

Cultural:

Biological:
There are no specific biological control methods for angular leaf spot.

Chemical:
Chemical controls are typically ineffective against this pathogen.



Red Stele
Phytophthora fragariae

Damage. Red Stele is not as important in California as it is in Eastern growing regions due to soil fumigation, raised beds, drip irrigation and lower rainfall. However, it is expected to increase as methyl bromide is phased out. The symptoms of this disease include severe stunting followed by death of plants. Optimum conditions for disease development occur when the soil is saturated. Zoospores (motile spores) swim to the roots and infect them. Well-drained soil and warmer soil temperatures, such as often occurs in California's growing regions, reduces and delays disease development. As a result, Red Stele represents only about 5% of the economic impact of phytophthora-based diseases in California. The incidence of this disease is expected to increase with the phase out of methyl bromide and the increased use of opaque mulches, which reduces soil temperature, for weed control.

Description of Infection. Symptoms first appear in plants located in low, poorly drained parts of the field. Plants become stunted as older leaves die and are replaced by smaller, younger leaves with short petioles. Young lateral roots are often completely rotted. New crown roots die from their tips back, producing a symptom called rat tail. Splitting the root reveals the red stele from which the disease gets its name.

Control

Cultural:

Biological:
There are no specific biological control agents against Red Stele.

Chemical:





Nematodes

It is important to note that all discussion related to nematode control are based on pest management strategies utilizing certified pest/disease free nursery stock growing in soil treated with methyl bromide/chloropicrin.



Foliar Nematode
Aphelenchoides fragariae

Northern Root Knot Nematode
Meloidogyne hapla

Symptoms and Damage. The presence of either foliar or northern root knot nematodes may result in plant stress and reductions in yield. Under current practices of fumigating strawberry fields with methyl bromide and chloropicrin and using certified nursery stock, these nematodes are rarely found to cause significant damage in California production areas. However, with the impending loss of methyl bromide and the increasing use of organic methods damage will likely become more common. Control of these two pests by nursery stock producers is critical because an infestation will prevent the grower from receiving government certification, thereby reducing the value of the planting stock.

Plant symptoms can be indicative of a nematode problem but are not fully diagnostic because similar symptoms could result from other problems as well. The symptoms may either be widespread or may appear in small patches within a field. Aboveground symptoms of foliar nematode include stunted growth, reddened leaves, small curled or crinkled leaves (crimp), deformed buds and flowers, and a reduction in flowering and fruiting. A reduction in flowering and fruiting may more reliably distinguish a foliar nematode infestation from insect infestations, which produce leaf symptoms similar to those described above. There are no reported below-ground symptoms with foliar nematodes. Aboveground symptoms of root knot nematodes include wilting during hot days, stunting, chlorosis, and suppression of fruit yields. Root galls formed near the root tips and abundant branching at and above the galls are the primary belowground symptoms of this pest.

Description of Pest. Plant parasitic nematodes are microscopic, unsegmented roundworms. The two species most commonly associated with damage in California strawberries are the foliar nematode, Aphelenchoides fragariae, and the northern root knot nematode, Meloidogyne hapla. Strawberries are also hosts for the following nematodes: root lesion (Pratylenchus penetrans), stem (Ditylenchus dipsaci), dagger (Xiphinema americanum), needle (Longidorus elongatus), foliar (Aphelenchoides ritzemabosi, Aphelenchoides besseyi), and root knot (Meloidogyne incognita and Meloidogyne javanica). All of these nematodes are potential pathogens to strawberries in California and their identification in strawberry plantings or in land to be planted to strawberries are cause for concern.

Monitoring. To make management decisions, a grower must monitor the field by taking soil and plant samples, sending them to a diagnostic laboratory for identification. Sampling and extraction techniques are typically 30 to 50% effective in detecting species that might be present.

Controls

Cultural:

Biological:
There are no known biological control agents that have been shown to control or suppress nematodes.

Chemical:





Weeds

Overview. The longer growing season of California strawberries results in a greater challenge to weed control. Effective weed management in strawberries requires a combination of cultural practices, preplant soil fumigation, and additional herbicide applications when necessary. Proper preplant field preparation and bed preparation are essential for a good weed control program. For weed and pathogen control, fumigation with a combination of methyl bromide and chloropicrin, or to a lesser extent metam sodium, in conjunction with plastic mulches, is a major method of weed control in California strawberries. A few growers in the warm Central Valley use soil solarization in place of preplant fumigation. For weeds that escape preplant controls, hand-weeding and/or selective herbicides are used. In some cases, organic mulches have been used instead of plastic ones.

Strawberries are highly susceptible to weed competition immediately after planting when the plants are small and frequent sprinkling provides ideal conditions for weed germination. Most weeds that invade strawberries are annuals. During stand establishment, little mallow bur, clover and sweet clover, and filaree are common weeds because their seeds survive fumigation. Once strawberries are in the bearing stage of growth, windblown weed seeds including sowthistle, common groundsel, and grasses may become problems. In certain sites, perennial weeds such as field bindweed, spurge, and bermudagrass may require control, especially in fields where the crop is carried over into a second year of production. In areas where strawberries are carried over for 2 years, weed management during the second winter consists of a combination of preemergence herbicides, mulches, and/or hand-weeding.

Growers select sites with good drainage in areas with good quality water. Fields are surveyed for perennial weeds. The broad-spectrum control of methyl bromide allows for the use of land that may have a weedy history, but less weedy sites are preferred. Certain weeds (such as hairy nightshade) host soil-borne diseases (such as Verticillium wilt). Treatment of these weeds, therefore, can result in a lower incidence of soil-borne diseases. During the early stages of plant establishment, growers must check frequently for weeds (at least once every 3 weeks during the first 3 to 4 months after planting). Weeding crews are sent through fields, as needed, to remove weeds.

The loss of methyl bromide in 2006, with incremental reductions of 25% in 1999, 50% in 2001, and 70% in 2003, will have a dramatic impact on the effectiveness of weed control in California's strawberries. Productivity losses are anticipated due to increasing competition for soil and sun and increased abundance of hosts for insect pests and diseases. Alternative fumigants, such as 1,3-D plus chloropicrin mixture and chloropicrin alone, are less active on weeds than methyl bromide. Therefore, weeding costs are likely to increase during and after the methyl bromide phase out.

Controls

It is important to note that all discussion related to weed control are based on pest management strategies utilizing certified pest/disease free nursery stock growing in soil treated with methyl bromide/chloropicrin.

Cultural:
Weeds can be controlled culturally through the use of mechanical methods or with organic and synthetic mulches.

Chemical:
For effective weed seed control it is essential, regardless of fumigant, that the soil be pre-irrigated so that weed seeds are saturated with water before fumigation and that soil temperatures be above 55F. The following fumigants are used for weed control.





Vertebrate Pests

Overview. A number of vertebrate species may move into or live near strawberry fields that seek the fields for food. The potential for damage by vertebrates varies from field to field and region to region. Some fields are much more susceptible to damage. Migratory and resident birds can cause significant damage. Fields located near rangeland, wooded areas or other uncultivated areas are more likely to be invaded or re-invaded by certain vertebrates. Predators, diseases and food sources all may influence vertebrate populations. Predators such as coyotes, foxes, snakes, hawks and owls feed on rodent and rabbit species. Growers cannot, however, rely on predators to prevent rodents or rabbits from becoming agricultural pests.



Birds

HOUSE FINCH: Carpodacus mexicanus
ROBIN: Turdus migratorius
GOLDFINCHES: Carduelis spp.
CEDAR WAXWING: Bombycilla cedrorum
STARLING: Sturnus vulgaris
LONG-BILLED CURLEW: Numenius americanus

Damage. Several species can cause severe damage when they feed on ripening fruit in strawberry fields. Economic losses can be reduced by using frightening devices or preventing access during the harvest season by placing netting over the field.

House finches are the most troublesome bird pest in strawberries. They are residents in all strawberry growing regions and may feed in strawberry fields whenever ripe fruit is present.

Robins are present in strawberry fields throughout the year in some parts of southern California. In other regions, flocks of robins visit fields during migration, usually in late winter or early spring.

Goldfinches are small, bright yellow birds that typically feed on weed seeds, but in fall or in late winter large flocks may invade strawberry fields to feed on the seeds of the strawberry fruit.

Cedar waxwings are shiny, buff brown birds that have a characteristic crest and black mask over the eyes. They may cause serious damage to strawberry production in the central coast region. Cedar waxwings move through fields in flocks of 20 to 50 birds during late winter and early spring migrations, destroying large quantities of ripening fruit.

Starling, in large migratory flocks, may invade strawberry fields in late winter or early spring to feed on ripe strawberries. Resident starlings may feed in strawberry fields any time ripening fruit are present.

Long tailed curlews move through fields on the central coast, Santa Maria Valley and Oxnard Plain regions in early spring. They are large birds with a wingspan of about 2 feet, that have long legs and are characterized by a long bill that curves downward at the tip. Curlews feed in flocks of 10 to 20 and tend to return to the same areas each spring.

Monitoring. The best strategy for reducing bird damage depends on the species feeding on the crop. Growers identify the birds that are causing damage before choosing controls. By keeping records of bird problems and the time of year they occur, helps growers to plan control actions.

Control

Cultural:



California Ground Squirrel
Spermophilus beecheyi

Damage. Ground squirrels can be a serious problem in strawberry fields when populations have built up in adjacent areas and invade the fields to feed on fruit. Squirrels may also feed on leaves and stems and sometimes damage polyethylene irrigation hoses.

Monitoring. Growers monitor for ground squirrels by checking the perimeter of the field about once per month for animals or their burrows. If monitoring indicates that a squirrel population is moving in, they can be controlled with traps, fumigants, or toxic bait.

Controls

Cultural:

Chemical:



Meadow Mice
Microtus spp.

Damage. Meadow mice, which are also referred to as voles or field mice, inhabit roadsides, meadows, canal banks, fence-rows and many field crops. When mouse populations reach high levels in their native grassy habitats, they invade and occupy neighboring strawberry fields, feeding on ripening fruit.

Description. Full-grown meadow mice are larger than house mice but smaller than rats. Well-established populations can be recognized by the network of small runways through the grass or other cover and the openings of numerous shallow burrows. Meadow mice are active year round, day and night.

Monitoring. Growers monitor the fields by visually inspecting fields looking for active runways and burrows. Snap traps baited with a mixture of peanut butter and oats are also used to monitor the mouse populations.

Control

Cultural:

Chemical:



Moles
Scapanus spp.

Damage. Moles may invade strawberry plantings anytime during the year, destroying planting beds with their burrowing activity. Moles feed primarily on earthworms and soil arthropods, which are destroyed by soil fumigation; therefore, moles are more likely to invade second-year and unfumigated strawberry fields. Moles construct shallow feeding tunnels, which are apparent as linear ridges on the soil surface, and a serious of deeper tunnels from which soil is pushed to the surface to form molehills. Molehills tend to be circular with a plug in the middle.

Description. Moles have cylindrical bodies with pointed snouts, dark, velvety fur, and spadelike front feet used for digging. They are active day and night and are rarely seen above ground.

Control

Cultural:



Mule Deer
Odocoileus hemionus

Damage. In northern California, mule deer sometimes enter nursery fields destroying young strawberry plants by feeding on them and trampling them. They feed on plants and fruit, in fruit production fields located near good deer habitat. Deer are most likely to be a problem from late spring to midsummer in low-elevation nurseries. Deer feed at night and early in the morning. Growers identify deer pests by footprints in the field and deer droppings.

Control

Cultural:





Research

With the impending loss of methyl bromide as a pest management tool, the strawberry industry faces the challenge of developing a sound, multi-faceted, reduced-risk approach to integrated pest management that will provide viable biological controls, cultural practices and chemical tools for disease, insect and weed control. The continued economic success of the strawberry industry in California will be based, in part, on the industry's ability to develop a pest management program that balances sound cultural and biological control practices with chemical treatment.

Research and development into alternate pest management systems that can substitute for the current uses of methyl bromide is clearly the number one future challenge and focus of the industries research efforts. Methyl bromide will no longer be available for use in 2006 and there are no comparable broad-spectrum tools available for control of soil-borne pests. Alternates to methyl bromide being assessed currently include the fumigants chloropicrin (alone), metam sodium, and 1,3-dichloropropene plus chloropicrin (TELONE C-35); however, substantial regulatory impediments exist for use of these methyl bromide alternatives. Chloropicrin alone is not permitted in certain counties within California. Metam sodium is under FQPA review by the United States Environmental Protection Agency and 1,3-dichloropropene is limited by township use and 300' buffer zones.

Narrow spectrum chemical tools are also being tested to substitute for parts of the wide array of pest control solutions that methyl bromide currently provides. For example, pesticides such as hexythiazox (SAVEY) may substitute for some of the miticidal properties of methyl bromide and herbicides may enhance the weed control activity of the methyl bromide alternatives. Examples of new soil-applied herbicides that may be used for this purpose are: carfentrazone-ethyl, flumioxazin, isoxaben and sulfentrazone. In areas where plastic mulches are not used, a post emergence herbicide, triflusulfuron, may be a useful treatment to explore. The development of a glyphosate resistant strawberry will be of limited value in California due to the extensive use of plastic mulches that prevent glyphosate application to weeds growing below the plastic.

Enhanced use of cultural techniques such as mulching, solarization and plant breeding are also being considered by the strawberry industry. It is clear that, for California's strawberry industry, many different chemical and cultural tools will be needed in the near future to substitute for this single pest management ingredient.

Other areas of particular research needs are the development of control methods for Western Flower Thrips, mites, and lygus bugs. Diseases of increasing concern to the industry include Verticillium wilt, phytophthora crown rot and root rot, and red stele though significant increases in the resistance of botrytis fruit rot to existing fungicides has triggered increasing research into new pest management tools and expanded use of IPM by the industry.





Contacts

Frank Westerlund (Overall Pest Management Contact)
California Strawberry Commission
41 Hangar Way, PO Box 269
Watsonville, California 95077
831-724-1301 ext. 434

Doug Gubler (Foliar Diseases)
Department of Plant Pathology
University of California at Davis
Davis, California 95616
530-752-0304

John Duniway (Soil Borne Disease)
Department of Plant Pathology
University of California at Davis
Davis, California 95616
530-752-0824

Steve Fennimore (Weeds)
Weed Science Program, Department of Vegetable Crops
University of California at Davis
c/o USDA
Salinas, California 93905
831-755-2896

Frank Zalom (Entomology)
UC Statewide IPM Program
University of California at Davis
Davis, California 95616
530-752-8350

Becky Westerdahl(Nematodes)
Department of Nematology
University of California at Davis
Davis, California 95616
530-752-1405

Kirk Larson (Pomology)
Department of Pomology
University of California at Davis
Davis, California 95616
949-857-0136



Reviewed by:

California Pesticide Impact Assessment Program
University of California, Davis
(530) 754-8378



CALIFORNIA STRAWBERRY COMMISSION
41 Hangar Way, P. O. Box 269
Watsonville, California 95077-0269

References